Procedure for the metered addition of copper ions in cheese production

ABSTRACT

For the metered addition of copper ions in cheese production in a stainless steel kettle 
     (a) CO 2  is introduced into the added water, 
     (b) copper ions are produced electrolytically in the added water by means of electrodes immersed in the added water, 
     (c) the enzymes necessary for the cheese production are added to the added water containing CO 2  and copper ions and 
     (d) the added water containing CO 2 , copper ions and enzymes is added to the raw milk for the cheese production. 
     An apparatus for carrying out this procedure is characterized by 
     (a) an electrolyzing tank (10) having an anode (11), a cathode (12) and a vent (13), 
     (b) means (1, 2, 3, 4, 6) for feeding added water into the electrolyzing tank (10), 
     (c) means (5, 7, 8, 9) for the metered addition of CO 2  to the added water, 
     (d) a mixing tank (16) having a mixing device (17), 
     (e) means (14) for draining the added water from the electrolyzing tank (10) into the mixing tank (16), 
     (f) means (15) for adding enzymes to the mixing tank (16), 
     (g) a milk kettle (19) having a mixing device (20) and 
     (h) means (18) for draining the added water from the mixing tank (16) into the milk kettle (18).

This application is a divisional application of Ser. No. 07/365,548filed on Jun. 13, 1989.

In Switzerland, hard cheese is traditionally produced from raw milk in acopper kettle. This results in problems, on the one hand, in cleaningthe copper kettles; since no acids or alkali solutions can be used, thecopper kettles have to be cleaned by hand. On the other hand, owing tothe relatively high copper content originating from the copper kettles,cheese factory butter has only a limited storage stability.

Since the beginnning of the fifties, attempts have therefore been madeto produce hard cheese, in paticular Emmentaler, in stainless steelkettles. However, the results were unsatisfactory since, as abiochemically active metal, the copper evidently has a favourable effecton the growth of the micro-organsims responsible for the flavourproduction and acid production and also on the activity of the ripeningenzymes. Practical experience shows that, in the production ofEmmentaler in a steel kettle, defects such as after-fermentation andpoor cheese taste occur owing to the absence of sufficient quantities ofcopper.

Attempts have therefore been made to add copper ions to the milk in theproduction of hard cheese in a stainless steel kettle. The meteredaddition of various copper salts has not proved successful since therequired copper (I) salts are not soluble but are readily converted intocopper (II) salts which do not have the same favourable effect on themicrobiological processes as the copper (I) salts. In addition, anunsuitable quantity of the copper salt may easily be added as a resultof weighing errors or the like. The electrolytic metered addition ofcopper ions using a copper anode which is immersed in the raw milk hasalso proved not to be feasible in practice since the milk coagulates atthe anode in a few minutes, as a result of which the electrolyticsolution of copper is completely prevented.

It has now been found that it is possible to carry out the electrolyticmetered addition of copper ions in the so-called added water, that is tosay, in the fresh water which is used to dissolve the enzymes for thecheese production. In that case, there is virtually no contamination ofthe electrodes.

At the copper anode, the copper first dissolves in the form of Cu (I)ions whose solubility can be increased by introducing CO₂ into the addedwater. In addition, the required expulsion of oxygen is promoted by theCO₂ dissolved in the water. Since, in general, micro-organisms whichthrive in an acid medium are involved in the microbiological processesof the cheese production, these processes are also promoted by the acidpH of the added water resulting from the introduction of CO₂.

The procedure according to the invention for the metered addition ofcopper ions in cheese production in a stainless steel kettle istherefore characterized in that CO₂ introduced into the added water,copper ions are produced electrolytically in the added water by means ofelectrodes which are immersed in the added water and of which the anodeis composed of copper and the cathode of copper of an inert metal, theenzymes necessary for the cheese production are added to the added watercontaining CO₂ and copper ions and the added water containing CO₂,copper ions and enzymes is added to the raw milk for the cheeseproduction.

0.1 to 10 g of CO₂ per liter of added water can be introduced. Thevolume of the added water is, as a rule, 0.1 to 10% of the volume of theraw milk. Expediently, enough copper ions are produced in the addedwater for the raw milk to contain 0.1 to 10 mg of copper ions per liter.For this purpose, electrolysis can be carried out for 1 minute to 2hours at a current level of 1 to 100 ampere.

The accompanying drawing shows an embodiment of an apparatus forcarrying out the procedure according to the invention.

In the drawing, the added water (fresh water) is fed in at 1. The freshwater feed can be shut off by means of a shut-off valve 2 and regulatedby means of a pressure regulating valve 3 and a solenoid-operated valve4. CO₂ can be introduced into the added water pipe 6 via the CO₂ pipe 9by means of the metered addition valve 5 from the CO₂ container 7 whichis fitted with a solenid-operated valve 8.

The added water pipe 6 opens into an electrolysing tank 10 in which ananode 11 and a cathode 12 are provided. The electrolyzing tank 10 isfitted with a vent 13 having a level switch; the level switch shuts offthe water and CO₂ feed when the electrolyzing tank has been filled andswitches on the electrolysis by means of a timing relay. The hydrogenproduced during the electrolysis is able to escape through the vent 13.

The solenoid-operated valve 14 can be used to drain the added watercontaining copper ions and CO₂ into the mixing tank 16 in which theenzymes necessary for the cheese production are added at 15 and which isfitted with a stirrer 17. The added water containing the copper ions,the CO₂ and the enzymes can be drained into a milk kettle 19, which isfitted with a stirrer 20, through the shut-off valve 18.

The entire procedure can be automatically controlled by means of acontrol box (not shown) so that incorrect operations are impossible.

The procedure according to the invention, which was carried out in theapparatus described above, is explained in more detail in the followingexamples.

EXAMPLES

A pushbutton switch is used to feed cold tap water (added water) via asoleniod-operated valve 4 through the pipe 6 into the electrolyzing tank10 which contains two copper electrodes 11, 12 and has a capacity ofV_(E). At the same time, CO₂ is fed into the added water in a quantityof M_(CO).sbsb.2 from the the CO₂ container 7 via a solenoid-operatedvalve 8, the pipe 9 and a metered addition valve 5.

When the electrolyzing tank 10 has been filled with the added watercontaining CO₂, the level switch incorporated in the vent pipe 13 shutsoff the water and CO₂ feed and switches the electrolysis on. The currentlevel I_(E) and the electrolyzing time t_(E) are adjusted in accordancewith the value of the copper concentration C_(Cu) to be reached in theraw milk.

After the electrolyzing time t_(E) has expired, the added watercontaining CO₂ and copper ions is drained via the solenoid-operatedvalve 14 into the mixing tank 16, mixed with the enzyme fed in at 15 bymeans of the stirrer 17 and drained via the shut-off valve 18 into themilk kettle 19 which has a capacity V_(M) and mixed therein with the rawmilk by means of the stirrer 20.

The values of V_(M), V_(E), M_(CO).sbsb.2, I_(E), t_(E) and C_(Cu) forExamples 1 to 5 are specified in the following table.

                                      TABLE                                       __________________________________________________________________________    V.sub.M  V.sub.E  M.sub.CO.sbsb.2                                                                   I.sub.E                                                                           t.sub.E                                                                            C.sub.Cu                                       Example                                                                            liters                                                                            % of V.sub.M                                                                       liters                                                                            g/liter                                                                           ampere                                                                            minutes                                                                            mg/liters of milk                              __________________________________________________________________________    1    10,000                                                                            0.1  10  9.5 50   1   0.1                                            2    40,000                                                                            0.5  200 10  100 40   2                                              3     2,000                                                                            2    40  8   10  60   6                                              4     1,000                                                                            7    70  0.1 4.2 120  10                                             5      200                                                                             10   20  0.7 1   90   9                                              __________________________________________________________________________

I claim:
 1. An apparatus for producing hard cheese using a process whichcomprises treating raw milk in a stainless steel kettle in the presenceof copper ions, enzymes necessary for cheese production and added waterto dissolve the enzymes, said apparatus comprising:(a) an electrolyzingtank having a vent and a means for introducing copper ions into addedwater comprising an anode and a cathode, (b) means for feeding addedwater into the electrolyzing tank, (c) means for adding a metered amountCO₂ to the added water, (d) a mixing tank having a mixing device, (e)means for draining the added water from the electorlyzing tank into themixing tank, (f) means for adding enzyme to the mixing tank, (g) a milkkettle having a mixing device, and (h) means for draining the addedwater from the mixing tank into the milk kettle.